Quantum entanglement shows that reality can’t be local

Either that, or faster-than-light communications is a go.

Quantum entanglement stands as one of the strangest and hardest concepts to understand in physics. Two or more particles can interact in a specific ways that leave them entangled, such that a later measurement on one system identifies what the outcome of a similar measurement on the second system—no matter how far they are separated in space.

Repeated experiments have verified that this works even when the measurements are performed more quickly than light could travel between the sites of measurement: there's no slower-than-light influence that can pass between the entangled particles. However, one possible explanation for entanglement would allow for a faster-than-light exchange from one particle to the other. Odd as it might seem, this still doesn't violate relativity, since the only thing exchanged is the internal quantum state—no external information is passed.

But a new analysis by J-D. Bancal, S. Pironio, A. Acín, Y-C. Liang, V. Scarani, and N. Gisin shows that any such explanation would inevitably open the door to faster-than-light communication. In other words, quantum entanglement cannot involve the passage of information—even hidden, internal information, inaccessible to experiment—at any velocity, without also allowing for other types of interactions that violate relativity.

Experiments have definitively demonstrated entanglement, and ruled out any kind of slower-than-light communication between two separated objects. The standard explanation for this behavior involves what's called nonlocality: the idea that the two objects are actually still a single quantum system, even though they may be far apart. That idea is uncomfortable to many people (including most famously Albert Einstein), but it preserves the principle of relativity, which states in part that no information can travel faster than light.

To get around nonlocality, several ideas have been proposed over the decades. Many of these fall into the category of hidden variables, wherein quantum systems have physical properties (beyond the standard quantities like position, momentum, and spin) that are not directly accessible to experiment. In entangled systems, the hidden variables could be responsible for transferring state information from one particle to the other, producing measurements that appear coordinated. Since these hidden variables are not accessible to experimenters, they can't be used for communication. Relativity is preserved.

Hidden variable theories involving slower-than-light transfer of state information are already ruled out by the experiments that exclude more ordinary communication. Some modern variations combine hidden variables with full nonlocality, allowing for instantaneous transfer of internal state information. But could non-instantaneous, faster-than-light hidden variables theories still work?

To investigate this possibility, the authors of the new study considered the possible experimental consequences. Obviously, one way to test it would be to increase the separation between the parts of the entangled system to see if we can detect a delay in apparently instantaneous correlation we currently observe. Sufficiently fast rates of transfer, however, would still be indistinguishable from nonlocality, given that real lab measurements take finite time to perform (this assumes that both experiments happen on Earth).

The researchers took a theoretical approach instead, using something known as the no-signalling conditions. They considered an entangled system with a set of independent physical attributes, some observable, some hidden variables. Next, they allowed the state of the hidden variables to propagate faster than the speed of light, which let them influence the measurements on the separated pieces of the experiment.

However, because of the nature of quantum mechanical systems, there was a symmetry between the hidden and measurable attributes of the system—meaning if the hidden variables could transfer information faster than light, then the properties we can measure would do so as well. This is a violation of the no-signalling condition, and causes serious problems for the ordinary interpretations of quantum physics.

Of course, one conceivable conclusion would be that faster-than-light communication is possible; this result provided a possible avenue for testing that possibility. By restricting the bounds on the speed of interaction between entangled systems, future experiments could show whether any actual information is traveling or not.

However, the far more likely option is that relativity is correct. In that case, the strong ban on faster-than-light communication would rule out the possibility of faster-than-light transfer of information encoded in hidden variables, and force us to deal with nonlocality. Once again, it would seem that local realism and relativity are incompatible notions in the quantum world.

Thank you for this article! as always they're informative and thought provoking.

When I read any article about quantum entanglement I'm always looking for a reason that a simple-minded explanation of the phenomenon is ridiculous: all objects entangled are the same object; and would be seen to be so if one could view down the 'correct' dimensional projection. Think of the flatland occupant that sees a single object as being two because it enters the 2d plane at two separate places.

This has to be wrong because it's too simple and therefore would have been immediately discounted - but why not a single mention of it (even in off-hand dismissal)?

thankee!

I'm with you (I think...).

The article says - "The standard explanation for this behavior involves what's called nonlocality: the idea that the two objects are actually still a single quantum system, even though they may be far apart." And that the most likely option is that relativity still holds and that it implicates non-locality.

Would also like to see some reasoning about why entangled objects could not be very same object. It's just a matter of how you see it, or?

I'm really surprised that no-one as mentioned many worlds so far. If many worlds is true, then quantum entanglement does not violate locality.

Many worlds is disgusting in its own way. Think about it: every single outcome possible under quantum mechanics, no matter how unlikely, is realized. There exists a Universe where, if it's Tuesday and you look up and to the left, every radioactive atom in your body simultaneously decays coupled with the fusion via very low probability tunneling of every hydrogen atom in your spleen, resulting in a massive thermonuclear explosion. That Universe is out there somewhere in Many Worlds, and it's no less likely than the exact one we live in (though the one we live in tends to look very similar to the average case, and let's hope it stays that way).

Well, it's not exactly as if The Great Minds have said: “God Playing Dice! Kewl! Time to move on to something unsolved!”

At least until you go deeper than casual thinking, “Many Worlds” is very tractable. When 538.com says Obama has a 73.6% chance of winning, Silver's stating his belief that for every 1000 possible November 7ths he might wake up into, Obama will have been re-elected in 736 of them, based on his understanding of how time unrolls. I'll guess that he's rather over-confident in his models, so the whole notion of “anything COULD happen” is helpful in dealing with ordinary reality as well as the little challenges here.

We know that voters Alpha and Beta have agreed to split their vote. Either Alpha votes R and Beta votes D, or vice-versa; we somehow know with certainty that we will be in one of those two alternate realities. When we learn that Alpha has voted D, we do NOT learn that Beta voted R; we learn which of the two constrained realities we had been in since the entanglement.

Yes, I could go thermonuclear, but in maybe only one of the many, many universes. I don't know how entangled all of my atoms are (aren't they ALL radioactive albeit with super-long half-lives?), but ordinary observation would suggest that they were mysteriously entangled; it'd be possible that a suicide decay pact among them, allowing only some to undergo decay during any given time frame. Hard to argue that we know all the entanglements if their mechanisms etc are so spooky.

So we don't need googol^googol^… alternate worlds; it seems that I recently read something like 10^200 (give or take a few orders of magnitude on the exponent; not too many more than 10^80, the number of atoms in the observable universe).

I'm really surprised that no-one as mentioned many worlds so far. If many worlds is true, then quantum entanglement does not violate locality.

Many worlds is disgusting in its own way. Think about it: every single outcome possible under quantum mechanics, no matter how unlikely, is realized

Exactly. The many worlds theory is flawed by it's human centric basis. When you extend it to what it logically would mean, its just silly. If there's nothing special about humans... then its not just our action or choices where all possibilies happen, its every living thing down to each individual cell, and extending from there it's every possible chemical reaction, and from there every possible quantum state of everything, since the beginning of the universe. Especially with growing research that the universe itself may not be infinite, infinite alternate universes just doesn't seem plausible.

IMO quantum entanglement indicates extra dimensions that we can't measure or interact with. To us, the particles may seem be seperated by great distance, but the part that is 'entangled' hasn't moved.

I don't know much about physics. That being said, why can't it just be as follows:

Analogy: take two boxes and put the same message in each. Separate the boxes a million light years. The instant you open each box, you will get the same message at each location, without FTL travel.

These aren't hidden variables necessarily, just variables which are set to the same values. Or maybe I'm misunderstanding, and these are hidden variables...

This is a good way to think about it, but the variables you're talking about ARE hidden. They aren't knowable from outside the boxes without opening them. This is much like knowing about the state of the quantum system, you have to take a measurement (open the box) to reveal what is hidden.

HOWEVER, there is a bit of a subtle difference WRT to quantum measurements. You don't know what the value of the message is, because until you measure it it literally HAS no definite value. This is where the questions about non-locality or FTL/near-FTL communications come in. By common sense when one of a pair is measured and takes on a definite value our intuition says the other half of the pair must learn about it SOMEHOW, there has to be a causal link. The problem is we can prove that there is either no causal link or a causal link that is non-local. Neither of those options sits well with physicists. IMHO though it is just a natural bias we have towards analog macroscopic thinking. In reality 2 entangled objects are like 2 sides of a single coin, it can only come up heads or tails, not both. Distance is simply not fundamental, spacetime is an emergent phenomenon.

These problems would go away if one insists that time has no dimension (which it doesn't) and space is not a "fabric" (which it ain't). Then entanglement and superposition are just two aspects of the same phenomenon. Both local space and non-local space are superpositioned on each other.

This happens even in the macro-world. Consider a space ship going to the nearest star at 86% the speed of light. Time dilation factor is ½. That is, an observer on Earth will witness clocks on the ship running at half the speed and an observer on the ship will see clocks on Earth running at half the speed. But distance is compressed along the path at relativistic speeds. The observer on Earth sees the ship is squashed along its motion of travel and the observer on the ship sees the Earth squashed along its motion of travel. But the observer on the ship also measures the distance to the nearest star to be half of that measure by the Earth observer. That is, two observers measuring the same distance come up with two different values. That is not a fabric. That is superposition. Space is a superposition; it can be two lengths at the same time.

Thank you for this article! as always they're informative and thought provoking.

When I read any article about quantum entanglement I'm always looking for a reason that a simple-minded explanation of the phenomenon is ridiculous: all objects entangled are the same object; and would be seen to be so if one could view down the 'correct' dimensional projection. Think of the flatland occupant that sees a single object as being two because it enters the 2d plane at two separate places.

This has to be wrong because it's too simple and therefore would have been immediately discounted - but why not a single mention of it (even in off-hand dismissal)?

thankee!

I think again you can think of 'non-locality' as meaning this. All non-locality means is that 2 things somehow interact over a distance without any regard for what is between them. You could consider this to be a sort of 'extra dimension' in which these objects are close to each other.

These problems would go away if one insists that time has no dimension (which it doesn't) and space is not a "fabric" (which it ain't). Then entanglement and superposition are just two aspects of the same phenomenon. Both local space and non-local space are superpositioned on each other.

This happens even in the macro-world. Consider a space ship going to the nearest star at 86% the speed of light. Time dilation factor is ½. That is, an observer on Earth will witness clocks on the ship running at half the speed and an observer on the ship will see clocks on Earth running at half the speed. But distance is compressed along the path at relativistic speeds. The observer on Earth sees the ship is squashed along its motion of travel and the observer on the ship sees the Earth squashed along its motion of travel. But the observer on the ship also measures the distance to the nearest star to be half of that measure by the Earth observer. That is, two observers measuring the same distance come up with two different values. That is not a fabric. That is superposition. Space is a superposition; it can be two lengths at the same time.

Entanglement involves superposition, but you don't need all the other stuff. Time is a dimension, it is necessary to specify events. Space is dimensions of relative position. The special relativity example shows time is not absolute with regard to space, it is not a quantum physics example, so has little to do with superposition.

What's to stop me from sending multiple dice, each in their own labeled boxes?

i.e. "Attack" "Report" "Return"

It'd be one way communication, but marching orders all the same.

Because you can't control the quantum state.

So you have your die, and purely by chance, your roll a "1". The other die MUST be a "6". But all you can do is roll the dice, and the results are always random.

The only "data" you can "send" is "I rolled a 3, then I rolled a 5, then I rolled a 1". But those are just random numbers. It’s random/useless information.

Not so fast.

Say we have two entangled coins. We agree upon a time at which we’ll flip the coins to reveal their state and agree that if heads comes up we will meet downtown for beers where-as if tails come up we agree to meet uptown for tequila shooters. We each take a coin and head home. Later we flip the coins at the agreed point in time, and instantly know where to go to meet the other person.

I'm really surprised that no-one as mentioned many worlds so far. If many worlds is true, then quantum entanglement does not violate locality.

Many worlds is disgusting in its own way. Think about it: every single outcome possible under quantum mechanics, no matter how unlikely, is realized. There exists a Universe where, if it's Tuesday and you look up and to the left, every radioactive atom in your body simultaneously decays coupled with the fusion via very low probability tunneling of every hydrogen atom in your spleen, resulting in a massive thermonuclear explosion. That Universe is out there somewhere in Many Worlds, and it's no less likely than the exact one we live in (though the one we live in tends to look very similar to the average case, and let's hope it stays that way).

Agreed. One wonders, are we actually experiencing one of many possible universes or the averaged results of all possible universes? It seems more like the later really. The really outre possibilities simply contribute so little that we effectively never notice them. Its only when we look at individual quantum effects that we have to notice that there are individual separate possibilities. As long as you never put cats in boxes you never get neither-dead-no-alive cats and you can happily go about your classical business.

We agree upon a time at which we’ll flip the coins to reveal their state and agree that if heads comes up we will meet downtown for beers where-as if tails come up we agree to meet uptown for tequila shooters. We each take a coin and head home. Later we flip the coins at the agreed point in time, and instantly know where to go to meet the other person.

These problems would go away if one insists that time has no dimension (which it doesn't) and space is not a "fabric" (which it ain't). Then entanglement and superposition are just two aspects of the same phenomenon. Both local space and non-local space are superpositioned on each other.

This happens even in the macro-world. Consider a space ship going to the nearest star at 86% the speed of light. Time dilation factor is ½. That is, an observer on Earth will witness clocks on the ship running at half the speed and an observer on the ship will see clocks on Earth running at half the speed. But distance is compressed along the path at relativistic speeds. The observer on Earth sees the ship is squashed along its motion of travel and the observer on the ship sees the Earth squashed along its motion of travel. But the observer on the ship also measures the distance to the nearest star to be half of that measure by the Earth observer. That is, two observers measuring the same distance come up with two different values. That is not a fabric. That is superposition. Space is a superposition; it can be two lengths at the same time.

Entanglement involves superposition, but you don't need all the other stuff. Time is a dimension, it is necessary to specify events. Space is dimensions of relative position. The special relativity example shows time is not absolute with regard to space, it is not a quantum physics example, so has little to do with superposition.

This is not something mysterious that needs magical explanation.

And what happens when a particle with mass is travelling so fast that all distances along its path are less than Planck length?

What you are doing is applying the old model, the one that doesn't explain entanglement. Without breaking it, you will never get an explanation for entanglement.

BTW, the explanation I gave was mathematical, not magical. It know they appear to be the same but magic needs a firm foundation in reality. Mathematics creates its own reality.

Except that entanglement isn't actually about getting a message at all. Following the message in a box example... imagine that they are perfectly preserved, then one box gets opened. It undergoes a change as it begins deteriorating. Simultaneously without the other box also being opened, the other message a million light years away, also begins deteriorating. When you look at the second message, you instantly know that the other message has been read because it has already begun deteriorating before you opened the box.

...Except that you won't actually be able to tell whether your box began decaying before you opened it, unless you get a phone call from your friend Wigner, who wants to know if your box is doing anything funny, because his sure is.

The "classical object in a box" analogy is this:

I put a red marble in one box and a black marble in the other box. Then have the department secretary send one to New York and one to LA without telling her which is which. When the recipient in NY opens the box, if he has a red marble he instantly knows that there is a black marble in LA and if he finds a black marble, he knows the red marble is on the west coast.

The two common fallacies are:1) That the west coast recipient will ever know what color marble he recieved without either opening the box, or getting a phone call from his east coast friend.

2) The whole "Let's use this for FTL communication" thing. If the East Coast recipient sprays black paint into the box before he looks at the marble, the marble on the West Coast doesn't magically turn red.

That's basically entanglement in a nutshell. Now let's look at the "quantum" part that people have issues with.

The entirety of the "quantum weirdness" is in the "indeterminate" or "superposed" state that exists prior to observation. Observation collapses the wavefunction for the observer, and also reveals similar information about the paired particle due to the correlated properties within an entangled system.

Compared to the classical example above what this does NOT do is:1) Collapse the wavefunction of either particle for non-observers who don't communicate with observers (and therefore become observers-by-proxy).2) Allow non-observational perturbations to the state of one particle influence the state of the other particle.

This idea has been kicking around in my head for about the last ten years, and this seems like as good a time as any to get it out there. Clearly there are much smarter people on this board that can help me understand if this experiment would work or not.

First lets start off with two sets of entangled particles, AB and CD.

Now lets separate the pairs in such a way as to maintain their quantum state and lets send A&D to one location and B&C to another location.

Let us now suppose that there is a question that we want answered. This is a simple yes or no question. If the answer is yes, A&D will be combined in such a manner that they become entangled, if the answer is no, A&D will be left alone.

It is my understanding, that if two halves of entangled pairs are combined, their former counter parts (B&C in this case) become entangled and that this entanglement can be verified experimentally.

Question 1. Are my initial assumptions true based on current science?Question 2. Would this "transmission" of the entangled state following the entanglement of A&D occur faster than the speed of light?Question 3. It would seem that if A&D and B&C were far enough apart, that this would permit information to be sent faster than the speed of light, (e.g. the answer to our yes or no question)

Question 4. The question that up to this point has always scared me about this topic. The above scenario assumes the careful timing of of question and answer. But what if we throw that timing out the window. What if A&D are inside Schrodinger's Box along with the mechanism that will entangle them if the particle decays and leave them alone if it doesn't decay. We now have no idea when to test B&C to determine the state of the particle. So if go ahead and test B&C and find that they are entangled (or not for that matter) have we in effect opened the box? Is it possible to have a disconnect between the results of B&C and A&D, regardless of how long we wait or the order we go in?

What's to stop me from sending multiple dice, each in their own labeled boxes?

i.e. "Attack" "Report" "Return"

It'd be one way communication, but marching orders all the same.

OK, suppose you send me these dice. How do the labels help? I now have a bunch of dice, you roll yours randomly and mine come up the same/opposite (whichever doesn't matter) and how does that tell me what you want or give me any information? Remember, you can't control the values of your dice, nor me the values of mine. I can know that certain of your dice came up certain values, and we might then pick a strategy to coordinate an attack say based on that, but we could have just as easily decided that with regular dice before we parted. Neither of use learns ANYTHING from these dice. It seems odd, but when you actually try to implement a communications channel that DOES SOMETHING you find you can't actually do anything that you couldn't do without the dice to start with.

We agree upon a time at which we’ll flip the coins to reveal their state and agree that if heads comes up we will meet downtown for beers where-as if tails come up we agree to meet uptown for tequila shooters. We each take a coin and head home. Later we flip the coins at the agreed point in time, and instantly know where to go to meet the other person.

Wait, I'm a little confused. Fundamentally, locality states that an object is influenced directly only by its immediate surroundings (usually seen through some particles transmitting forces in the Standard Model from one physical body to another). So if you reject that, you can have something changing something else at a distance, without the use of some intervening system of particles, waves, or other form of medium. So far, so good (sort of).

But does that necessarily mean that faster-than-light communication is possible? If by manipulating A I can change B at some arbitrary distance through no intervening force, particle, or other object of any kind, then I can cause an effect that travels faster than light. And that contradicts relativity right there. Einstein formulated relativity the way he did because he believed in locality. If you throw out locality, doesn't relativity (at least, the part that assumes FTL communication is impossible) go along with it?

An interesting note is that, up until quantum mechanics came on the scene, every scientist did just about everything possible to avoid breaking locality. Everyone held that it was inviolable (Newton even going so far as to say it was impossible for any man competent in rational thinking to hold nonlocality as possible). I, for one, think it far more likely that FTL communication is possible. But, I've been wrong before, once or twice.

Locality is simply an observed property of the physical macroscopic universe. The relationships between objects are largely determined by the physical distances between them. Newton simply stated that it would be irrational because EVERYTHING he could see around him supported the notion that locality was absolute. He was simply being rational.

In terms of Relativity it isn't so much that it is built AROUND locality as that locality is axiomatic in any theory of space and time. Space (at least) is ALL ABOUT locality. The limitations on velocity are simply a consequence of the way relativity is structured. They arise out of the nature of the underlying space and time. It isn't a priori necessary that information can't travel faster than light (and in some solutions of GR this does happen), just that if you have such things happening then you lose causality and conservation laws, and effectively lose locality as well. Ultimately you have theory of nothing at that point.

The thing is, none of this really talks to whatever 'deeper reality' there would be in say a holographic universe, one where other universal variables exist that mediate interactions which are non-local. Again, since GR/SR don't forbid the passing of information at faster than light these things aren't incompatible, they just force you to give up notions like absolute causality and absolute global conservation laws (they actually do exist, but not in the sense we normally think of).

Thank you for this article! as always they're informative and thought provoking.

When I read any article about quantum entanglement I'm always looking for a reason that a simple-minded explanation of the phenomenon is ridiculous: all objects entangled are the same object; and would be seen to be so if one could view down the 'correct' dimensional projection. Think of the flatland occupant that sees a single object as being two because it enters the 2d plane at two separate places.

This has to be wrong because it's too simple and therefore would have been immediately discounted - but why not a single mention of it (even in off-hand dismissal)?

thankee!

They are the same object, but if this is due to higher geometry that's yet to be demonstrated. Two particles that are "linked" by the same wave function, that are part of the same quantum system, are the same object. What's hard to grasp is that it may not be turtles all the way down from there. It's simply how reality works at the quantum level. So when measurement observes one and we find that the other has the same state, that's mind blowing but it's essentially no different than looking at a single coin and saying "this coin is facing heads up, just like itself".

In our "macro" world where classical physics is still quite useful, we can look at two coins, no matter how preciesly minted to be identical, and it's clear there are two different objects in classical physical and human perception terms. But photons have much fewer characteristics than coins; there is tremendously less information needed to describe them. Make their characteristics identical and make them part of the same quantum system and voila, a single object. That's why distance is irrelevant. But it's also tenous as measurement breaks the entanglement. Since measurement can be even the slightest interference, we don't see entaglement happening randomly with macroscopic objects. The odds are overwhelmingly against it.

So, simple in a way, confirmed by Bell's Theorem and by experiment, but we are so unaccustomed to thinking of the world in this manner that it seems there must be some "trick" going on.

What's to stop me from sending multiple dice, each in their own labeled boxes?

i.e. "Attack" "Report" "Return"

It'd be one way communication, but marching orders all the same.

If you're looking for a particular option to be chosen from among the orders (say, by doing whichever box contained a die with a 1 up-face), there's no way for me to set the die value on my end (I can only roll the die), so you'd be more or less choosing a random set of orders.

No problem with picking on my post - feedback is always important when coming up with analogies .

So really the crux of the issue is being able to manipulate the quantum state without breaking the entanglement.

So why can't a measurement be seen as simply entangling ourselves with the particles being measured?

That would involve combining you and the system into one wavefunction in superposition, which is impossible. Measurement is the environment impinging on the wavefunction and causing it to decohere.

Actually see the Relational and Transactional Interpretations of QM, which essentially provide various ways of looking at this. Relational Interpretation is particularly interesting in that it points out that, much like entropy, entanglement is a relative thing and you can't really state that a waveform is or is not collapsed in any absolute sense. All of these statements can only make sense relative to some other quantum object.

So why can't a measurement be seen as simply entangling ourselves with the particles being measured?

That would involve combining you and the system into one wavefunction in superposition, which is impossible. Measurement is the environment impinging on the wavefunction and causing it to decohere.

Relational Interpretation is particularly interesting in that it points out that, much like entropy, entanglement is a relative thing and you can't really state that a waveform is or is not collapsed in any absolute sense.

Perhaps the particle is not far away from the other entangled particle because they are both essentially everywhere at once until you observe them? It might appear they act local when they aren't, because in their superposition they are local until observed.

This makes me think of the game "Red Light, Green Light". The "Traffic Light" doesn't know where any of the "cars" are, and they could be anywhere, because it is not observing them. As soon as "red light!" is called, their positions become fixed so long as they are being observed.

So the big step left here is to affect the probability of measuring a state on a quantum object with some sort of external phenomena and determine if the particle remains entangled? In Schrodinger fashion, we toss the box around a few times before opening it. (disclaimer, I love cats despite being allergic).

What's to stop me from sending multiple dice, each in their own labeled boxes?

i.e. "Attack" "Report" "Return"

It'd be one way communication, but marching orders all the same.

Because you can't control the quantum state.

So you have your die, and purely by chance, your roll a "1". The other die MUST be a "6". But all you can do is roll the dice, and the results are always random.

The only "data" you can "send" is "I rolled a 3, then I rolled a 5, then I rolled a 1". But those are just random numbers. It’s random/useless information.

Not so fast.

Say we have two entangled coins. We agree upon a time at which we’ll flip the coins to reveal their state and agree that if heads comes up we will meet downtown for beers where-as if tails come up we agree to meet uptown for tequila shooters. We each take a coin and head home. Later we flip the coins at the agreed point in time, and instantly know where to go to meet the other person.

So what? You haven't really exchanged any information at that point, it was all exchanged beforehand when you agreed on the choices. You could just as easily have flipped a regular coin then and you'd be no more or less better informed than you are now. There is no SUPERLUMINAL CONDUIT of information here. You've delayed a local choice, but you already have all the information needed to make that choice on hand the whole time. Nothing need be communicated at the moment of flipping your magic coins.

Physicists need to read "Flatland" by Edwin Abbott Abbott. Read and understand how the two dimensional beings freak out whenever a three dimension object passes though their reality.

A three dimensional ring passing though a two dimensional world (like a wedding ring passing though a piece of paper perpendicularly) appears at first to be one particle then splits into two (and these two "particle" appear to have no connection in the two dimensional world) yet tap one and the other shakes (the particle are "spookly" entangled to the two dimensional beings), then the two particles recombine and disappear.

Quantum entanglement looks exactly like an object in in another dimension passing through our "normal" dimensions. Everything from spooky non-locality to spontaneous particles jumping into and out of reality, is easy to understand if an extra "quantum" dimension is imagined.

No, no, no. It isn't physicists that need to read Flatland. It's you who needs to read physics. The whole point of this article, and the whole issue with hidden variables, relativity and locality, is that quantum entanglement does *not* look exactly like an object in another dimension blah blah blah.

If quantum entanglement behaved as you suggest, then the correlation between the remote entangled objects could be used to do FTL communication. It has been demonstrated time and time again both theoretically and experimentally that you can't do that. What you described is equivalent to the FTL hidden variable scenario that this article is about, and they've shown that it doesn't match reality.

This is the biggest misunderstanding that so many people have about remote entanglement. It IS NOT *just* about two things changing simultaneously over arbitrary distances. The true difficulty is about the bizarre fact that the simultaneity detected is only visible after *classical* information about the measurement at one end has been propagated classically at non-FTL speeds to the other end and compared. You CANNOT detect the "simultaneous" change at the other end without slow classical communication between them. That would not be true if what you say is true.

What's to stop me from sending multiple dice, each in their own labeled boxes?

i.e. "Attack" "Report" "Return"

It'd be one way communication, but marching orders all the same.

If you're looking for a particular option to be chosen from among the orders (say, by doing whichever box contained a die with a 1 up-face), there's no way for me to set the die value on my end (I can only roll the die), so you'd be more or less choosing a random set of orders.

To go with the dice analogy, in order to set the value of my die's up-face to a 6, I first have to see what face is currently facing up, then turn the die so the 6 is pointing up. However, that first check of the initial state will break the entanglement.

No problem with picking on my post - feedback is always important when coming up with analogies .

So really the crux of the issue is being able to manipulate the quantum state without breaking the entanglement.

We can't do that, because in order to manipulate the state to a known value (required for information transfer) we first have to know what the state is - which will break the entanglement.

Quantum mechanics is the Ptolemaic astronomy of the twentieth century: an elaborate mathematical representation of a flawed paradigm.

Quantum mechanics is the bete noire of armchair "experts" the world around, who deign to make grand pronouncements about it despite their vast lack of knowledge about it.

The *elaborate* mathematical represention of quantum mechanics is used because NO ONE HAS COME UP WITH ANYTHING SIMPLER THAT MATCHES THE VAST NUMBER OF EXPERIMENTAL RESULTS. Until *you* come up with a theory that is simpler and testably better, then any spouting off about "flawed paradigms" is nothing but hot air.

What's to stop me from sending multiple dice, each in their own labeled boxes?

i.e. "Attack" "Report" "Return"

It'd be one way communication, but marching orders all the same.

If you're looking for a particular option to be chosen from among the orders (say, by doing whichever box contained a die with a 1 up-face), there's no way for me to set the die value on my end (I can only roll the die), so you'd be more or less choosing a random set of orders.

No problem with picking on my post - feedback is always important when coming up with analogies .

Eh. I think I was being too literal, and forgetting you can't observe the dice in real time to watch for a change.

What's to stop me from sending multiple dice, each in their own labeled boxes?

i.e. "Attack" "Report" "Return"

It'd be one way communication, but marching orders all the same.

If you're looking for a particular option to be chosen from among the orders (say, by doing whichever box contained a die with a 1 up-face), there's no way for me to set the die value on my end (I can only roll the die), so you'd be more or less choosing a random set of orders.

No problem with picking on my post - feedback is always important when coming up with analogies .

So really the crux of the issue is being able to manipulate the quantum state without breaking the entanglement.

Or perhaps at least being able to detect whether entanglement has been broken without disturbing that entanglement. So, in the theory involving three orders, you check the entanglement status of all three and whichever is broken becomes your order because it has been broken from the other end...? Not exactly efficient communications, but it would function in a very limited way.

This idea has been kicking around in my head for about the last ten years, and this seems like as good a time as any to get it out there. Clearly there are much smarter people on this board that can help me understand if this experiment would work or not.First lets start off with two sets of entangled particles, AB and CD.

Now lets separate the pairs in such a way as to maintain their quantum state and lets send A&D to one location and B&C to another location.

Let us now suppose that there is a question that we want answered. This is a simple yes or no question. If the answer is yes, A&D will be combined in such a manner that they become entangled, if the answer is no, A&D will be left alone.

It is my understanding, that if two halves of entangled pairs are combined, their former counter parts (B&C in this case) become entangled and that this entanglement can be verified experimentally.

Question 1. Are my initial assumptions true based on current science?

Ahh, but how do you entangle A&D at will without breaking the AB and CD correlations? For example, if A&B are electrons with spins correlated by the Pauli exclusion principle and C&D have a similar correlation, how do you force A&D into a spin correlation without breaking one (or both) existing correlations?

Even if you could do that, there are issues. For example, using 4 photons with circular polarization correlations for AB and CD, and linear polarization correlation for AD--you still have to tell the guy with the BC pair whether entanglement means parallel or perpendicular polarizations, so you rely on plain old subluminal communication to relay the same amount of information.

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Question 2. Would this "transmission" of the entangled state following the entanglement of A&D occur faster than the speed of light?

Even if it did, here's the kicker: It would be transmitted from the CD pair to you, not the other way. Someone at the other end would have no way of knowing whether the particles were entangled unless you told them what to look for.

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[Question 3. It would seem that if A&D and B&C were far enough apart, that this would permit information to be sent faster than the speed of light, (e.g. the answer to our yes or no question)

Actually, if AD and BC are *any* distance apart. This is pretty much the only step so far that's not equivalent to "and then a miracle happens."

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Question 4. The question that up to this point has always scared me about this topic. The above scenario assumes the careful timing of of question and answer. But what if we throw that timing out the window. What if A&D are inside Schrodinger's Box along with the mechanism that will entangle them if the particle decays and leave them alone if it doesn't decay. We now have no idea when to test B&C to determine the state of the particle. So if go ahead and test B&C and find that they are entangled (or not for that matter) have we in effect opened the box? Is it possible to have a disconnect between the results of B&C and A&D, regardless of how long we wait or the order we go in?

The problem is, entanglement doesn't work the way you (and many people) seem to think. It's not "if I poke A, then B wiggles", it's "if I found A, then the other one out there must be B. Or vice versa." Quantum mechanics just adds a range of indeterminate states in between, like "I think this is probably A, so there's probably a B somewhere else."

The thing about those indeterminate states is, you can collapse the wavefunction by observation, but you can't know ahead of time which way it will collapse.

{Offtopic, but kinda related: It's hard to explain quantum mechanics to people outside that area. There's a horrible human tendency to conflate things we don't understand, and while it leads to some amusing "Bigfoot is an extraterrestrial race returning their Atlantean colony" type conspiracy theories, the genuine weirdness of quantum mechanics tends to horribly diluted (and even overshadowed) by mysticism in many of the books written for the layman. I highly recommend reading some very boring textbooks on the subject, and rolling your eyes at anyone who implies a sheet of photographic film is "conscious" because it observes and records the location of a photon.}

So really the crux of the issue is being able to manipulate the quantum state without breaking the entanglement.

Or perhaps at least being able to detect whether entanglement has been broken without disturbing that entanglement. So, in the theory involving three orders, you check the entanglement status of all three and whichever is broken becomes your order because it has been broken from the other end...? Not exactly efficient communications, but it would function in a very limited way.

The only way to "check" if the entanglement is broken is to do a measurement - which breaks it.